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Strain Relaxation in Heteroepitaxial Si1-xGex Films via Surface Roughening Processes

Published online by Cambridge University Press:  21 February 2011

Cengiz S. Ozkan ,
William D. Nix  and
Huajian Gao
Cengiz S. Ozkan
Affiliation:
Stanford University, Materials Science and Engineering Dept., Stanford, CA 94305
William D. Nix
Affiliation:
Stanford University, Materials Science and Engineering Dept., Stanford, CA 94305
Huajian Gao
Affiliation:
Stanford University, Mechanical Engineering Dept., Stanford, CA 94305
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Abstract

Surface roughening associated with strain relaxation of Si1-xGex films grown epitaxially on (100) Si substrates has been investigated using transmission electron microscopy, atomic force microscopy and x-ray diffraction. Epitaxial films 100 Å in thickness and containing 18% Ge, which are subcritical with respect to the formation of misfit dislocations, show strain relaxation through surface roughening on annealing at 700 °C. Enhanced surface grooves aligned along <100> directions are observed in films annealed at 850 °C. Strain relaxation as measured by x-ray diffraction is significantly greater at the higher temperature. Prolonged anneals at 850 °C also result in islanding. The surface roughening processes have also been studied in subcritical films with 15% Ge at 900 °C. These films also show enhanced grooving aligned along <100> directions. These observations are consistent with an anisotropic elastic analysis which indicates that grooving should occur preferentially along <100> directions. Intermixing effects in these samples have also been investigated through depth profiling using Auger Electron Spectroscopy. In addition to the above subcritical films, other films with 18% and 22% Ge and supercritical thicknesses have also been studied. For these films, surface grooving is observed along <110> directions, which suggests that these grooves are related to the formation of misfit dislocation networks. The role of these surface roughening processes in the nucleation of dislocations has also been explored.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 399: Symposium D – Evolution of Epitaxial Structure and Morphology , 1995 , 407
Copyright
Copyright © Materials Research Society 1996

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References

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